Ethernet switch maker Force10 Networks has closed a $75 million round of funding, as it readies itself for a public offering next year.

This is the fourth round of funding for Milpitas, Calif.-based Force10, bringing the total money raised so far to almost $290 million, the company said Monday. Andrew Feldman, vice president of marketing for the company, said he expects this to be the last round of private funding for the company. He expects Force10 to file for an initial public offering with the U.S. Securities and Exchange Commission sometime next year.

"With this money, we can choose the timing of an IPO on our own," he said. "We don't have to be forced into anything. It gives us an enormous pool of resources to build the company."

The company would not officially disclose its valuation, but a source close to Force10 said venture backers valued it at more than $400 million.

Unlike most start-ups these days, Force10 has real customers and revenue. The company has already won nearly 80 customers, including big names like Google, ESPN, NASA, MCI, China Telecom and NTT, according to a recent research note published by Tim Luke, an equities analyst at Lehman Bros. He estimated that the company is currently pulling in about $10 million in revenue per quarter and is on target to break even in the first quarter of 2005, with about $20 million to $25 million in revenue.

Founded in 1999, Force10 was the first company to sell an Ethernet switch that could forward packets of data at 10 gigabits per second. At about that time, switch vendors such as Cisco Systems, Extreme Networks and Foundry Networks only had products that could forward traffic at a maximum speed of 8gbps. These companies have since followed Force10's lead with the introduction of second- and third-generation products that forward packets at the higher rate.

A 10gbps Ethernet switch is designed for use in the guts of a network to aggregate lower-speed data streams. Immediate demand for the switches is in corporate data centers, where companies are using them to cluster several high-speed servers.

The market is growing and is likely to continue growing rapidly, as prices fall. At the end of 2002, the year that the 10gbps Ethernet standard was ratified, equipment makers sold only about $42 million worth of equipment, according to The Yankee Group. By the end of last year, the market grew to roughly $90 million.

Force10 has about 275 employees. Meritech Capital Partners and Morgenthaler co-led the latest funding round. Crosslink Capital joined as a new investor, while existing investors U.S. Venture Partners, New Enterprise Associates and Worldview Technology Partners also contributed.